On a normal vehicle wheel and tyre assembly, the beads of the tyre sit in ‘seats’ of the wheel rim and, when the tyre is inflated, internal air pressure holds the beads in place.
In the event of a tyre deflation whilst a vehicle is in motion the tyres beads can move inwards from the wheel rims seats. When this occurs, grip between the tyre and the wheel rim is decreased. This can allow the tyre to slip circumferentially around the wheel and as a consequence the vehicle loses traction, as the wheel can rotate within the tyre and its beads, or the vehicle can loose braking efficiency as the rotation of the wheel may be stopped by the vehicles brakes while the tyre continues to rotate.
There are devices, variously known as ‘well fillers’, available to prevent tyre beads slipping into the wheel's well, but these do not stop the tyre moving circumferentially round the wheel rim when running deflated due to the well filler of necessity being of a lesser diameter than the wheel's seats and therefore the tyres beads. It is necessary for well filler's to be of a smaller diameter than the wheel's seats and the tyres beads otherwise it would be impossible to fit the tyre to the wheel. These devices are not designed to lock the tyres beads into place on the wheel rim and therefore the tyre may move circumferentially around the wheel rim, therefore traction and braking control may be compromised.
There are devices, variously known as ‘runflat assemblies’ or ‘runflat devices’ that may be fitted to a single piece drop centre wheel rim. These may have a diameter greater than the seats and the flanges of the wheel rim and be of sufficient diameter to support the tread of the tyre when running flat. Generally the base of these devices, where they fit and come into contact with a single piece drop centre wheel rim, have a small footprint area as space has to be left in the wheel's well to allow the tyres outer bead to be fitted when fitting the tyre. As the wheel's well is not completely filled and the device sits on a small footprint area stability of the runflat device may be compromised when the vehicle is running with a deflated tyre. The device can be forced sideways within the wheel's well in extreme runflat situations. In systems using an annular base fitted with a second outer ring, or segments forming a ring, which may rotate when the vehicle is running on a flat tyre, the small footprint area available to support the second or rotate-able ring or annular segments is narrow, reducing the capability of spreading the rotational forces and vehicle weight over a larger area and reducing pressure between the rotating parts. High pressures over a small contact area increase friction, which produces heat, reducing the devices longevity and therefore runflat distance capability. These devices can not lock the tyres beads in place in the wheel rims seats, therefore although the tyre may be supported when running flat, traction and braking may be compromised as the tyre is able to slip circumferentially around the wheel rim. Most current runflat devices take a long time to fit, relative to fitting the tyre, and for fitting require extra tools or equipment in addition to the tyre fitters normal tools and equipment.
There are devices variously known as ‘bead lock’ or ‘bead retention devices’ but these can not be fitted inside a single piece drop centre wheel rim as it has proven impossible to fit the tyre to the wheel rim in conjunction with one of these devices.
The present invention attempts to overcome the above problems faced in the known art and thus provides a method and system for fitting a runflat device to a vehicle wheel.